Hydrojet propulsion unit for water craft



y 18, 1955 G. R. ASCHAUER 3,183,878

HYDROJET PROPULSION UNIT FOR WATER CRAFT Filed Feb. 27 1963 2 Sheets-Sheet l INVENTOR. 65026-5 Z 1450/0052 BY ATTOENEY! y 1965 G. R. ASCHAUER 3,183,878

HYDROJET PROPULSION UNIT FOR WATER CRAFT Filed Feb. 27, 1963 2 Sheets-Sheet 2 I NVENTOR. GEO/Q65 Z fija/fldae B 22. si

A rive/v5 United States Patent 3,183,878 HYDROJET PRQPULSION UNIT FUR WATER CRAFT George Ii. Aschauer, Racine, Wis, assignor to Twin Disc Clutch Company, Racine, Wis., a corporation of Wisconsin Filed Feb. 27, M63, Ser. No. 261,282 8 (Ilairns. (Q1. 11516) This invention relates generally to marine jet propulsion for water craft and includes an improved centrifugal vane type feeding mechanism for-the jet nozzles.

A jet propulsion system fundamentally consists of a jet unit-usually an axial, radial or mixed-flow pumpdriven by a conventional engine. The marine jet operates on the reaction principle, the pressure inside the unit is unbalanced by lack of pressure at the open neck, and the craft is propelled forward in obedience to Newtons third law of motion: for every action, there is an equal and opposite reaction.

In conventional jet units, water is drawn through an inlet duct, usually in the hull bottom, is accelerated by an axiallow pump, and is ejected at the stern, either below or above the water surface. It is presently believed that no measurable difference in thrust efiiciency exists as between where the discharge occurs.

There are three general categories of jet pumps; the axial flow, the centrifugalor radial-flow, and the mixed flow. The rotating impellers, of a multi-stage axial flow type for example, generate pressure by forcing water into a path almost parallel with the rotating shaft. This axial flow type involves a minimum of restraightening of the flow path and produces good water acceleration.

The conventional centrifugal types also use rotating impellers, but force the water outward at nearly right angles to the rotating shaft. This flow must then be rebent to direct it aft to the thrust producing discharge nozzle, and this results in an inefficient system for jet boat propulsion.

Mixed-flow types include a wide range of pumps in which flow is both radial and axial.

Many of the prior art devices impart a rotary or spinning movement to the water resulting in a lateral thrust component which reduces etliciency. Attempts have been made to straighten out or unscrew this flow, usually in the nozzle itself, by means of flow directing shrouds, even having a reverse twist.

Accordingly, the present invention provides an improved jet nozzle feeding mechanism of the centrifugal pump type, which eliminates the rotary or spinning movemerit of the water being forcibly fed to the nozzle.

More specifically, the improved propulsion unit provided by the present invention has a centrifugal vane type feeding device which draws in the water, greatly accelerates and delivers it to the nozzle, all with the water flow path being in a gentle curve and without twisting or spinning movement being imparted to the water. This device is capable of delivering large volumes of water and an increase in mass flow results in increased ethciency. This flow to the nozzle at an increased speed and pressure, and the water velocity resulting from this pressure head drives the boat in a particularly efficient manner.

The jet drive provided by this invention results in a decreased velocity ratio of the jet to the boat, consequently directly resulting in a higher propulsion efiiciency, in accordance with the formula $.l83,878 Patented May 13, 1965 where VJ is the velocity of the jet with respect to the boat, and VB is simply the velocity of the boat.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings, in which:

FIGURE 1 is a fragmentary, side elevational view, in section, and showing the invention as embodied in one type of boat;

FIGURE 2 is a plan view of the FIGURE 1 device, certain parts being shown in section or broken away for clarity;

FIGURE 3 is a side elevational view of a modified form of the invention used with a boat, certain parts being shown as broken away and in section;

FIGURE 4 is a fragmentary rear View of the FIGURE 3 device, taken along line 44 in FIGURE 3 but on an enlarged scale, and with certain parts shown as broken away and in section;

FIGURE 5 is a side elevational view of still another modification of the invention, certain parts being shown as broken away or in section;

FIGURE 6 is a fragmentary plan view of the FIGURE 5 device, certain parts shown as broken away and in section, and

FIGURE 7 is a rear elevational view of the unit shown in FIGURES 5 and 6.

Referring generally to the form shown in FIGURES 1 and 2, this embodiment involves an inboard engine E which drives a centrifugal vane type pump P located within a conduit C passing through the boat B. Water is drawn through a water intake opening 1 at the bottom of the boat, is pumped through the conduit by the pump and is exhausted in a stream from the rear of the boat and above the waterline. The water as it is ejected astern as a free jet has a horizontal velocity which propels the boat forwardly.

Referring in greater detail to the FIGURE 1 form of the invention, the jet propulsion unit U includes a housing I-I located in the boat adjacent the stern thereof. This housing forms a Water duct that extends from below the surface of the waterrearwardly and upwardly in a gentle smooth curve. The water intake opening 1 at the bottom end of the duct may have an intake strainer 2 fixed thereover. When the invention is used with a boat of the type that floats in the water, or rides substantially on the water surface, the intake opening is preferably arranged to be substantially flush with the bottom of the boat so as to reduce turbulence in that area, and it is known that maximum jet speed is reached when the hull drag equals jet thrust.

Care must be exercised in the hull and intake design, however, to prevent excessive air from being drawn along the hull bottom into the jet intake, which causes overspeeding and power loss. For this reason it may be desirable that the intake opening be arranged at a slight angle to the horizontal so as to provide a positive scoop for the intake water. In any event, the intake opening is below the water surface over which the craft travels.

The housing also has a discharge opening 3 which faces rearwardly to communicate with a jet nozzle N which may be of the general type shown in my co-pending US. application Serial Number 207,642, filed July 5, 1962 and entitled Jet Propelled Water Craft; the nozzle in the present application, however, is wider so as to be co-extensive with the housing. Reference may be had to the said co-pending application if deemed desirable, but it is believed sufiicient to say that the nozzle receives water from the centrifugal pump P at a considerable pressure and the nozzle discharge opening area is variable by an adjustable baffie 4. Steering can be effected mes es by diverting some of the water out one or the other of the side openings 5. Reversing is accomplished by directing the flow out both of the forwardly directed openings 5a. Other types of nozzles having tail pipes with various steering quadrants and/ or special deflectors, may be employed with the present invention.

The housing has a generally cylindrical interior surface 6 which is disposed horizontally and also transversely in respect to the fore and aft direction of the boat. The generally cylindrical chamber which is formed by surface a is in fluid communication with the intake duct portion 7 of the housing and with the discharge opening, and this chamber together with a sliding vane rotor to now be described, defines the centrifugal vane type pump P.

The centrifugal vane rotor 8 is mounted within the cylindrical chamber on its shaft 9 which forms a horizontal transverse axis. This rotor has a series of radially slidable vanes 10 which cooperate with the interior surface of the housing to form a centrifugal vane type pump that draws water through the intake opening and forces it in a smooth flow path, as indicated by the arrows, and forcibly discharges it through the nozzle. The housing and its cooperating rotor may be of any desired length and the nozzle may also be of various corresponding lengths. The arrangement shown in FIGURE 1, however, where the nozzle is co-extensive in length with the vane pump, minimizes the turbulence as compared to an arrangement where the pump is longer than the nozzle.

FIGURES 3 f0 4 Referring now to the form of the invention as shown in FIGURE 3, as applied to an outboard motor, the propulsion unit Ua has the conventional clamping means 2!) for rigidly securing the unit to the transom. A power head in the form of an internal combustion engine Ea furnishes driving power through the drive shaft 21, bevel gear 22 and bevel gear 23 fixed on shaft 2d, meshing gears 25 and 26, and to shaft 27 of the vane rotor 28.

The intake opening 32 is located substantially flush with the boat bottom and at the bottom end of the rearwardly and upwardly inclined intake duct 33, which forms part of the housing Ha.

The housing has a generally cylindrical chamber 37, in which the vaned rotor 28 is mounted by its horizontal shaft 27. The rotor includes the radially slidable vanes 35 which bear against the interior surface of the chamher to form a centrifugal vane type pump Fa. A jet nozzle 34 is located at the rear of and in communication with the pump Pa.

The pump draws Water through the intake opening, moves it in a substantially straight path and without imparting any twisting movement thereto, builds up the water velocity and pressure and then forcibly discharges water through the nozzle to propel the craft.

Both of the previously mentioned forms of the invention illustrate the pump as operative about a horizontal axis but the invention is also applicable to a centrifugal vane type pump which is operative about a vertical axis. Such a further modification will now be referred to in connection with FIGURES 5, 6 and 7.

FIGURES 5, 6 and 7 This embodiment shows an inboard water craft having a power plant Eb which furnishes driving power through shaft 39 to the centrifugal pump Pb. The propulsion unit Ub functions to feed the water in a smooth curve and without imparting a twisting or spinning motion to the fiow path of the water.

Hydrofoil crafts may be of various designs, such as for example, the surface piercing foil type, the underwater foil type, and with or without surface-skimming stabilizer foils. The type shown in FIGURES 5 and 6 illustrate one form of the invention as utilized in one type of hydrofoil craft which has a main body 40 that rides above the surface 41 of the water under normal conditions when foil-borne. The main foils 42 and 43 are fixed, generally widespread V-shaped wings which curve under the boat bottom for the breadth of the hull. When foil-borne under normal conditions, these foils are only partially submerged, as shown.

A housing 47 is located in the main body ill of the craft and has a forwardly and downwardly inclined intalre member or duct 48 which terminates beneath the water and has a water intake opening 59. The lower portion 48:: of the duct flares outwardly so as to reduce its depth in the water but still maintainthe area of the intake duct larger than the discharge opening 52 to be described. The upper portion 48b of the duct is of some width in a fore and aft direction and is relatively narrow in a transverse direction so that a generally vertical wall of water is delivered upwardly in a smooth curve and into vertically arranged cylindrical chamber 51 in the main portion of the housing.

The housing also includes a rearwardly directed discharge opening 52 above the water surface, and a free jet nozzle 53 is in communication with that opening.

The generally cylindrical chamber 51 is located between and in communication with the intake duct and the discharge opening. This chamber is also located Recapizulazion The marine jet propulsion system of the present invention has been shown as of the free jet type discharging above the Water surface.

In any of the embodiments of the invention, the propulsion unit is located adjacent the stern of the craft and has a water intake opening below the surface of the water; the water is delivered to the jet nozzles rearwardly and upwardly and in a substantially straight line without imparting any appreciable rotary motion to the flow path. This centrifugal vane type pump is capable of etliciently handling and delivering large volumes of water without creating any appreciable turbulence.

The particular pump used in the presentinvention substantially eliminates any lateral components of thrust and is able to substantially decrease the velocity ratio of the jet to the boat, and thereby obtain more favorable propulsion efliciencies.

' Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

1 claim:

1. In combination with a water craft, a marine jet propulsion unit mounted for discharge'rearwardly of the craft and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit having a water intake opening below thesurface of the water and a rearwardly directed free jet nozzle located above the waterline, a Water duct extending without any sharp turns from said opening to said nozzle, and a high speed centrifugal sliding vane type pump in said duct and having its rotational axis positioned in a transverse direction and constructed to greatly accelerate and feed water through only a small portion of the total circumferential travel of said vanes in said pump and in a substantially straight line, whereby no spinning movement is imparted to the flow path of the water passing through said unit, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft. I 2. In combination with a water craft, a marine jet propulsion unit mounted for discharge rearwardly of the craft and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit comprising, a forwardly and downwardly inclined intake duct with a water intake opening below the surface of the water, a rearwardly directed free jet nozzle located above the waterline, a housing extending without any sharp turns between and in communication with said duct and said nozzle, and a high speed centrifugal sliding vane type pump in said housing and having its rotational axis positioned in a transverse direction in respect to a fore and aft direction of said craft, said pump being constructed to greatly accelerate and feed water through only a small portion of the total circular travel of said vanes in said pump and in a substantially straight line, whereby no spinning movement is imparted to the flow path of the water passing through said unit, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft.

3. In combination with a boat, a marine jet propulsion unit mounted for discharge rearwardly of the boat and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit having a water intake opening below the surface of the water over which the boat moves, said unit also having a rearwardly directed jet nozzle located above the water to act as a free jet, a water duct extending rearwardly and upwardly from said intake opening and having a discharge opening in communication with said jet nozzle, and a high speed centrifugal vane type pump in said duct and acting to draw water through said opening, greatly accelerate said water and build up a pressure head of said water and increase its velocity and forcibly discharge it through said jet to propel said boat, the flow path of the water through said unit being in a gentle curve and without any rotary movement, said pump and said jet nozzle being of a width which is at least one-half'of the width of the stern of said water craft.

4. In combination with a boat, a marine jet propulsion unit mounted adjacent the stern of the boat and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit comprising, a forwardly and downwardly inclined intake member having a water intake opening below the surface of the water, a rearwardly directed jet nozzle located above the water to act as a free jet, a water duct leading from said intake opening and having a discharge opening in communication with said jet nozzle, and a high speed vane rotor rotatably mounted in said duct and forming a centrifugal vane type pump with the interior of said duct to draw water through said opening, greatly accelerate said water and build up a pressure head of said water and increase its velocity and forcibly discharge it through said jet to propel said boat, the flow path of the water through said unit being in a gentle curve and without any rotary movement, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft.

5. A marine jet propulsion unit of the type operating on the reaction principle of the pressure Within the unit being unbalanced by lack of pressure at its discharge opening, said unit including a generally cylindrical housing adapted to be horizontally mounted on and transversely in respect to a water craft and having a forwardly and downwardly extending water intake duct with an intake opening below the surface of the water, said housing also having a rearwardly facing discharge opening above said water surface, a rearwardly directed free jet nozzle in communication with said discharge opening to receive in said housing and cooperating with the cylindrical 1 internal surface thereof to form a rotary vane type centrifugal pump which draws water through said intake opening, greatly accelerate said water and builds up a pressure head of said water and forcibly discharges it through said jet nozzle to drive said water craft, the flow path of water through said unit being in a gentle curve and without any appreciable spinning movement, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft.

6. In combination with a boat, a marine jet propulsion unit mounted adjacent the boat stern and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit including a generally cylindrical housing horizontally mounted transversely in respect to the boat, said housing having a forwardly and downwardly extending Water intake duct with an intake opening below the surface of the water, said housing also having a rearwardly facing discharge opening above'said water surface, a rearwardly directed free jet nozzle in communication with said discharge opening to receive water therefrom, and a high speed centrifugal vane member rotatably mounted on a horizontal transverse axis in said housing and cooperating with the cylindrical internal surface thereof to form a rotary vane pump which draws water through said intake opening, greatly accelerates said water and builds up a pressure head of said water and forcibly discharges it through said jet nozzle to drive said boat, the flow path of water through said unit being in a gentle curve and without any appreciable spinning movement, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft.

7. In combination with a boat, a marine jet propulsion unit mounted adjacent the boat stern and of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said unit including a housing having a downwardly and forwardly projecting water intake duct with an intake opening below the surface of the water, said housing also having a rearwardly facing discharge opening above said water surface, a rearwardly directed free jet nozzle in communication with said discharge opening to receive water therefrom, said housing having a generally cylindrical interior surface disposed horizontally and transversely and placing said intake opening in communication with said discharge opening, and a high speed centrifugal vane member rotatably mounted on a horizontal transverse axis within said generally cylindrical surface and cooperating therewith to form a rotary vane pump which draws water through said intake opening, greatly accelerates the water and builds up a pressure head of said water and forcibly discharges it through said jet nozzle to drive said boat, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said water craft.

8. In combination with a boat, a marine jet propulsion unit including a housing mounted in the boat and adjacent the stern, said .unit being of the type operating on the reaction principle of the pressure within the unit being unbalanced by lack of pressure at its discharge opening, said housing having a forwardly and downwardly projecting water intake duct with a bottom end which is substantially flush with'th-e boat bottom, said end having an intake opening below the surface of the water, said housing also having a rearwardly facing discharge opening above said water surface, the cross sectional area of said intake duct being greater than that of said discharge opening, a rearwardly directed free jet nozzle in communication with said discharge opening to receive water therefrom, said housing having a generally cylindrical interior surface disposed between and in communication with said intake duct and said discharge opening, and a high. speed centrifugal vane member rotatably mounted within said interior surface and cooperating therewith to form a rotary vane pump which draws Water through said intake opening, greatly accelerates the Water, builds up a pressure head of said Water and forcibly discharges it through said jet nozzle to drive said boat, said pump and said jet nozzle being of a width which is at least one-half of the width of the stern of said Water craft.

References fired hy the Examiner UNITED STATES PATENTS 115,425 5/71 Boyman 11516 3,034,295 5/62 Hanley 115-12 X 3,052,093 9/62 Keriefick -2; 1l5--12 X 3,055,175 9/62 Clark 11516 X FERGUS s. MIDDLETON, Primary Examiner. 

1. IN COMBINATION WITH A WATER CRAFT, A MARINE JET PROPULSION UNIT MOUNTED FOR DISCHARGE REARWARDLY OF THE CRAFT AND OF THE TYPE OPERATING ON THE REACTION PRINCIPLE OF THE PRESSURE WITHIN THE UNIT BEING UNBALANCED BY LACK OF PRESSURE AT ITS DISCHARGE OPENING, SAID UNIT HAVING A WATER INTAKE OPENING BELOW THE SURFACE OF THE WATER AND A REARWARDLY DIRECTED FREE JET NOZZLE LOCATED ABOVE THE WATERLINE, A WATER DUCT EXTENDING WITHOUT ANY SHARP TURNS FROM SAID OPENING TO SAID NOZZLE, AND A HIGH SPEED CENTRIFUGAL SLIDING VANE TAPE PUMP IN SAID DUCT AND HAVING ITS ROTATIONAL AXIS POSITIONED IN A TRANSVERSE DIRECTION AND CONSTRUCTED TO GREATLY ACCELERATE AND FEED WATER THROUGH ONLY A SMALL PORTION OF THE TOTAL CIRCUMFERENTIAL TRAVEL OF SAID VANES IN SAID PUMP AND IN A SUBSTANTIALLY STRAIGHT LINE, WHEREBY NO SPINNING MOVEMENT IS IMPARTED TO THE FLOW PATH OF THE WATER PASSING THROUGH SAID UNIT, AT LEAST ONE-HALF OF THE WIDTH OF THE STERN OF SAID WATER CRAFT. 